The invention relates to a process for aligning a glass fiber forming part of an optical transmission cable with an opto-electronic component. Problems arise at two portions of prior art processes:
(1) At the transition of the light between an emitting or receiving diode and an optical fiber portion, also sometimes called "mixing fiber", situated in an opto-electronic head which forms a terminal point of the optical transmission cable.
(2) At the passing point between two optical fibers, particularly in the case of connection between an optical transmission cable and an opto-electronic head.
The need for very high precision in the alignment results from the following considerations, where the difficulties met with are also set forth.
The diameter of the glass fiber of the optical cable is often very small, i.e. for example 125 microns, and in addition the "core" of the fiber, the only part used for effective transmission, is for example 50 microns in so-called "telecommunication" fibers. It is then necessary to carry out the alignment within a few microns, if possible within two or three microns.
In an opto-electronic reception head, there is an incorporated fiber portion which may have a head diameter greater than 50 microns but the head must remain small with respect to the useful area of the semiconductor diode, which is itself very small in the case of very-high-frequency connections.
In an emitting opto-electronic head, the diameter of the core of the fiber portion must be at least equal to the diameter of the emitting surface of the light-emitting diode so as to collect all of the light. That is to say, its diameter may be very much less than 100 microns.
In the connection between a cable and a head, the optical fiber of the cable is centered in an end-piece whose external contour forms a reference surface for positioning the axis of the fiber. The fiber portion incorporated in the head is centered by means of a fiber-holder, itself incorporated in the head. Between the end-piece and the fiber-holder there exists an adapter.
Known solutions to the alignment problem use either very-high-precision mechanical constructions or a manual positioning system integrated with the connecting device. They are generally complex and expensive.